With such rapid changes in marketing over the past several years, it shouldn’t come as a surprise that the meanings of various terms and practices would change as the field of web marketing expands. SEO (search engine optimization) and SEM (search engine marketing) are both terms that, in the past, were used somewhat interchangeably. Now they are used to describe two different practices.
In present parlance SEM has come to strictly mean paid search. It refers to any form of paid search advertising and includes pay per click (PPC), cost per click (CPC), and tools such as Google AdWords and Bing Ads. SEM is a way of paying to get into a top SERP spot and begin seeing an immediate impact on traffic.
Much of the work of SEM takes place off-page.
Meanwhile, SEO refers to organic, or natural, search and is the practice of selecting relevant keywords and using them in on-page content and code to draw in traffic from search engines. SEO also depends on building links to and from relevant sites. The impact on traffic is gradual, building over time.
SEO is heavily geared toward on-page tactics.
There is at least one point of overlap between SEO and SEM; both depend on a sound keyword strategy.
Details of Differentiation
A workshop listing and agenda from the October 2013 Search Marketing Expo (SMX) illustrates the difference in focus between the SEM and SEO tracks.
Product Listing Ads (PLAs) for e-commerce
Google AdWords and Bing Ads
Retargeting and geotargeting
Content writing for calls to action in ads
Mobile search ads
Cost per Action/Acquisition (CPA)
PageRank and search ranking factors
IP Detection / Redirection
301 and 302 Redirects
HTTP Headers/Crawler Access
As you can see, the SEM track is heavily focused on paid search practices while the SEO track is weighted toward the "classic" SEO tactics you should be familiar with.
Why You Should Care
Understanding industry jargon can prevent some expensive surprises. Like any good business person, you want to know exactly what you are getting for your investment in search marketing. If you hire someone who calls her/himself an SEO, [s]he may not have the tools or expertise for setting up the PPC campaigns you really wanted.
Before you hire a consultant, contractor, or employee for your search marketing efforts, decide what your expectations are. Do you need someone to help you build links or write web content with selected keywords? Or are you looking for someone to help you set up a pay per click campaign?
If the consultant promotes her/himself as an SEO, ask for a detailed listing of services [s]he performs. The same for someone promoting her/himself as a search marketer or SEM. This isn’t to say that one person can’t do both, but you need to be sure your expectations are met. Don’t sign a contract until you both agree on what practices will be implemented and exactly what work will be done.
The same reasoning holds true for workshops, webinars, and other educational services. If you or your employees need a basic grounding in using keywords in your HTML tags, you need to pay for educational opportunities in SEO, not SEM.
Finally, your SEO informs your SEM strategy. Understanding this will help you balance your search marketing budget and point you in the right direction for your search marketing efforts.